Collagen is widely used as a base material for a pharmaceutical product or a cosmetic product, as a biocompatible material for regenerative medicine or drug delivery system, and as a support for tissue culture and the like. Currently available collagen is mainly those obtained by purifying collagen from animals such as pigs and cattle. However, in the case where collagen derived from livestock is applied to humans, a risk of prion infection which may cause BSE has become a problem. Alternatively, collagen derived from plants or fish skin has started to be used, however, it involves a risk of gelatin allergy caused by intake of heterologous collagen. Accordingly, supply of a safe substitute for collagen has been demanded. Recently, construction of genetically engineered human collagen-produced system using various host organisms has been attempted, although it has not come into practical use yet.
Collagen has a structure in which three polypeptide chains form a long triple helix. It is well known that three chemically synthesized peptides having a collagen-like sequence are self-assembling to form the same triple helix structure as collagen, and such structures are used in studies of the structure of natural collagen. Collagen-like polypeptide known in the art include, for example, a polypeptide composed of a repeating unit comprising a peptide unit: [-(Pro-Y-Gly)n-]a (wherein Y represents Pro or Hyp and n represents an integer of 1 to 20) and a peptide unit, [-(Z)r-]b (wherein Z represents a peptide chain composed of 1 to 10 amino acid residues and r represents an integer of 1 to 20)(JP-A-2003-321500). Known supramolecules composed of a collagen-like peptide sequence include, for example, a collagen triblock peptide of Martin et al.: (Glu)5(Gly-X-Hyp-Gly-Pro-Hyp)6(Glu)5 (SEQ ID NO: 7) (Martin, R. et al., Biopolymers 70, 435-444, 2003) and a “peptide-amphiphile” of Fields (Fields, G B, Bioorg. Med. Chem. 7, 75-81, 1999).
However, there has been no report of a supramolecule which is formed through the intermolecular formation of complementary triple helix extending the molecule in the direction of triple helix axis.
An object of the present invention is to provide a polypeptide having a collagen-like triple helix structure and a peptide unit for producing such a polypeptide.